Underground storage tanks for holding a variety of liquids are well known. The most common use of storage tanks are those which are buried underground in gasoline service stations. Such tanks 10 normally contain at least ten thousand gallons of liquid. A typical service station will have anywhere from two to eight such tanks. A fill port at ground level is used for filling the tanks. An individual tank can have its own fill port and fill pipe, though most multiple tank systems will have one fill port which is inter- connected with all of the underground storage tanks. The tanks are continually being emptied and of course have to be refilled. A conventional transport truck is used for the refilling operation. Thus, access will be gained to the fill port and gasoline contained in the transport tank is unloaded by gravity feed into the underground storage tanks.
Leaks from defective underground storage tanks have occurred and have been well documented. Numerous attempts have been made in recent years to rectify the situation. Another lesser problem with underground storage tanks is in the careless filling of the tanks from the transport truck. The fill operation is such that it is possible for gasoline from the transport truck to be accidentally spilled onto the ground. These spills can be minor or can be rather substantial. Even minor spills over a length of time will build up and pose a significant environmental problem. Very little attention has been given to the problem associated with the fill operation. However, this too is an area of concern which must be addressed.
There is a need for better containment of the fill pipe of underground storage tanks. The known systems designed to contain spillage are adequate to a certain extent. However, there is still a need for a containment system which confines any spillage as well as encloses the fill pipe. There is also a need to continually monitor the system. Accidental spills are known when they occur. However, a slow leak through the fill pipe itself will most likely go undetected until substantial damage has occurred. In accord with this demonstrated need, there has been devised a containment assembly for use on underground storage tanks. The assembly is readily adapted for use on existing storage tanks. It solves many of the problems heretofore experienced.